The envelopes of color cathode ray tubes (CRT's), of the shadow mask type often employed in color television applications, are conventionally fabricated as an integration of neck, funnel and face panel components. The glass face panel includes a viewing area, having a patterned cathodoluminescent screen interiorly formed thereon, and a perimetrical sidewall therearound. The interior of the panel, including the screen and the surrounding panel sidewall, is usually metallized with a film deposition, such as aluminum, after formation of the screen. This metallic film serves two functions: first, it provides a portion of the electrical conductive path for the screen potential, and second, it provides an efficient reflective film upon the back of the screen thereby enhancing the frontal brightness thereof. Spatially positioned within the panel component is a multiple-apertured mask component formed to have a substantially domed areal foraminous portion, the surrounding edge of which is peripherally bonded to a rigid circumscribing framing member. This composite mask assembly, often referred to as a shadow mask, is supported within the panel, in spaced relationship to the viewing area and the coated surrounding sidewall, by a plurality of suitable positional means attached to the framing member in a manner to mate with supporting studs embedded in and projecting from the sidewall of the panel.
Upon completion of the screen fabricating procedure, the aforedescribed mask-panel assembly is hermetically sealed to the funnel component of the envelope. Electron generating means in the form of an integrated assembly comprising one or more electron guns, is then positioned and sealed within the neck component of the envelope, whereupon the tube is subsequently evacuated, sealed and processed.
In shadow mask CRT's, the conventional operating screen potential is substantially that of the final anode electrode of the electron gun assembly, such being achieved by a diverse internal conductive path within the envelope. The final anode electrodes of the gun assembly usually make electrical contact through associated supportive snubber means with an electrically conductive coating, such as Aquadag, which is applied to at least a portion of the interior surface of the funnel component of the envelope. Usually, the highest operating potential is applied to this conductive coating by means of a button-type connection oriented through the wall of the funnel. The other differential potentials necessary for the successful operation of the electron guns in the assembly, are supplied to the respective electrodes therein by specific electrical conductive means terminating at the connective pins or leads traversing the closure portion and base of the tube.
The final anode potential, supplied to the conductive coating on the interior surface of the funnel, is connected to the apertured mask by at least one resilient electrical contact member affixed to the mask framing member and suitably extended therefrom to make pressured contact with the funnel disposed coating.
Exemplary electrical connection between the mask and screen components of the assembly is accomplished through the spaced-apart mask positioners conjunctively functioning with the mating mast-supporting studs proturding from the panel sidewall and the metallized film disposed thereon. The stud members are usually kept free of aluminum film deposition to avoid possible deleterious flaking of the metallic film resultant from subsequent mask positioning in the panel. Since the mask positioning means per se make riding contact on the wall-oriented mask supporting studs, electrical connection between the mask and the aluminized sidewall of the panel is provided by applying an area of an additional conductive coating, such as Aquadag, to the basal portion of at least one of the studs proper making overlapping contact with the adjacent aluminum film to insure an electrical connection between the stud and the metallized sidewall of the panel. Since application of this discrete localized area of Aquadag is usually a manual operation, requiring cognizance to achieve a proper deposition of coating, there have been occasions of inherent human inconsistency when the quality of the coating deposition was somewhat wanting. Faulty coating application resulted in either a prevalence of flaked or particlized coating in the vicinity of the screen and mask or an electrical connection of a quality less than desired. In addition, there was a tendency for the coating to puddle thereby accentuating the danger of accidental splattering of Aquadag on the screen.
Another means for achieving an electrical connection between the mask and panel components of the mask-panel assembly, which eliminates the need for the extra Aquadag coating, is in the form of a resilient contactor of the general type substantially disclosed in U.S. Pat. No. 3,931,541, assigned to the assignee of this invention. This referred-to connective means is substantially comprised of an attachment portion affixed to the mask framing member wherefrom integral flexural and contact portions are oriented in a manner to extend forwardly therefrom toward the screen, in the spacing existent between the mask assembly and the conductive panel sidewall. There have been instances when hurried or somewhat careless insertion resulted in undesired abrasion of the panel disposed aluminum film thereby resulting in some loss of contact surface and the possible generation of deleterious particlized material in the screen and mask regions. The present invention is addressed to means for effecting beneficial temporary retractive positioning of a forwardly oriented contactor of substantially the general type described.